1. Field of the Invention
The present invention relates to a decorative plate having superior appearance by having a decorative groove carved thereon, a method of manufacturing the same, and a decorative article and timepiece using the decorative plate.
2. Description of the Related Art
Conventionally, a dial plate used for a wristwatch has been produced with a thin plate material of 0.4 mm thickness, such as a plate made from brass, in order to minimize the overall thickness of the wristwatch.
Specifically, in order to produce the dial plate, after the thin sheet-shape plate material is formed in a shape corresponding to the design of the wristwatch body and a center hole for inserting a driving shaft for driving the pointer is formed at the center thereof, a leg for securing to a movement is attached by welding etc.
Subsequently, the surface of such dial plate is ground and polished, and, after a decorative pattern such as radial pattern, moirxc3xa9 pattern, matrix pattern or spiral pattern is formed thereon by press stamping etc., the dial plate is plated and is colored by coating a paint including a pigment on the plating as necessary, which is further finished with clear coating.
And finally, a time and minute graduation for indicating time is printed thereon and a metal abbreviated character as a separate body is bonded to finish the dial plate.
In the spiral pattern, among the above decorative patterns, a pattern having a spiral groove is formed by moving a cutting edge, such as cemented carbide tool provided on a lathe, in a diametric direction of a rotary table while rotating the dial plate fixed to the rotary table to carve a groove of approximately 0.012 to 0.05 mm pitch and approximately 0.05 mm depth in spiral.
The pattern formed by a spiral groove has an appearance like a phonograph record without an uneven pitch and, since the groove works as a diffraction grating, reflected light varies in attractive rainbow colors according to the visual angle.
Such pattern formed by a spiral groove can be used not only for the dial plate of a wristwatch, but also as a decorative plate of knob of furniture or of an electric appliance, or as a decorative plate of accessories such as a necklace, cuff links or necktie pin.
However, such conventional decorative plate is planar and lacks a three-dimensional effect since it is produced from a thin plate, even when such pattern formed by spiral groove is provided, so that depth and luxurious touch cannot be afforded.
The three-dimensional effect can be created by forming the decorative plate in convex and concave lens or in Fresnel lens-shape. However, when the decorative plate is formed in a lens-shape, the thickness thereof may increase, thus making it difficult to be produced from a thin plate material.
Especially, a decorative plate used for a dial plate of wristwatch is extremely difficult to produce when the thickness of the dial plate is increased due to restrictions in design and production of the wristwatch.
Alternatively, a thick plate material may be three-dimensionally shaped using a NC carving machine etc. However, in this case, the thickness of the decorative plate and production cost thereof can increase greatly.
An object of the present invention is to provide a decorative plate having a three-dimensional effect, depth and luxurious touch even when produced from a thin plate, a method of manufacturing thereof, and a decorative article and timepiece using the decorative plate.
A first aspect of the present invention is a decorative plate including: a decorative portion carved with a decorative groove extending in spiral from inside toward outside of the decorative plate, the decorative groove being formed in a cross section of V-shape and including a non-equilateral portion where a slant angle of one of a pair of slanted sides forming the V-shape is different from a slant angle of the other slanted side.
According to the above first aspect of the present invention, by making the slant angle of an inner slanted side forming the V-shape of the decorative groove gentler than an outer slanted side at an inner part of the spiral, since the action of light reflected on the flat surface of the dial plate macroscopically becomes similar to the light reflected on a bulging surface, the central portion of the dial plate appears to be bulging. Accordingly, the decorative portion can achieve a three-dimensional effect even when the dial plate is made of thin plate.
On the other hand, by making the slant angle of an inner slanted side forming the V-shape of the decorative groove steeper than an outer slanted side, since the action of light reflected on the flat surface of the dial plate macroscopically becomes similar to the light reflected on an indented surface, the decorative portion can appear indented, thereby also achieving a three-dimensional effect even when the dial plate is made of thin plate.
The material of the decorative plate may be metal such as copper, bronze, German silver and aluminum, synthetic resin, glass, shell such as mother of pearl black and mother of pearl and precious stone, and composite material made by attaching thin plates of the above materials.
In the above decorative plate, the slant angles of the pair of slanted sides of the decorative groove may preferably vary gradually from the inner part of the spiral toward the outer part to be equal at the outer part.
Accordingly, when the slant angle of the V-shaped slanted sides vary greatly, the surface can be shown in steeply inclined manner and the slant angle is shown gentler as the slant angles of the V-shaped slanted sides become closer to each other.
For instance, when a decorative groove where the slant angle of the inner slanted side of the spiral is gentler than the outer slanted side and the slant angles of the slanted sides become gradually equalized from the inner part of the outer part of the spiral is provided on the disk-shaped material plate, a decorative plate having apparently greatly bulging central portion and flat peripheral portion as shown in FIG. 1 can be obtained.
On the other hand, when a decorative groove where the slant angle of the inner slanted side of the spiral is steeper than the outer slanted side and the slant angles of the slanted sides become gradually equalized from the inner part of the outer part of the spiral is provided on the disk-shaped material plate, a decorative plate having apparently greatly dented central portion and flat peripheral portion as shown in FIG. 2 can be obtained.
By forming such decorative groove, even when the decorative plate is made of thin plate, an apparent greater thickness relative to actual thickness thereof can be exhibited even when the decorative plate is made of thin plate.
In the above decorative plate, a decorative plating layer may preferably be provided at least on the decorative portion and the plating step for forming the decorative plating layer on the decorative portion may preferably be conducted after the carving step for carving the decorative groove.
By thus forming the decorative plating layer on the decorative portion, even when the decorative plate is made of synthetic resin, a three-dimensional effect can be achieved on the decorative plate by providing the decorative portion on the decorative plate.
When a precious metal layer having superior corrosion resistance is used as the decorative plating layer, even when an easily-carved metal of inferior corrosion resistance such as brass is used as the material of the decorative plate, superior corrosion resistance can be applied to the decorative plate and beautiful appearance can be maintained for a long time and the decorative groove can be easily carved on the decorative plate.
The decorative plating layer may be formed by silver, gold, rhodium and nickel.
In the decorative plate, a colored coating layer including a pigment may preferably be provided at least on the decorative portion and the coating step for forming the colored coating layer including the pigment on the decorative portion may preferably be performed after carving step for carving the decorative groove.
When the thickness of the colored coating layer is reduced, the effect of the decorative groove is not impaired and a variety of decorative plates can be obtained by preparing a plurality of different colors of paint for forming the colored coating layer. Further, since the colored coating layer can protect the decorative portion, weather resistance of the decorative portion can be improved, thereby maintaining the effect of the decorative groove for a long time.
Further, when a see-through paint is used as a paint for forming the colored coating layer and the color of apparently indented portion is thickened, the three-dimensional effect created by the decorative groove can be further emphasized.
In the above decorative plate, a transparent coating layer including no pigment may preferably be provided at least on the decorative portion and the transparent coating step for forming a transparent coating layer including no pigment on the decorative portion may preferably be performed after the carving step for carving the decorative groove.
The advantage of the decorative groove is not impaired at all when the transparent coating layer is thickly formed so as to completely cover the decorative groove provided on the decorative portion inside the coating layer.
Accordingly, the entire surface of the decorative plate including the decorative portion can be made flat by forming the transparent coating layer, thereby facilitating printing and setting time-indicating abbreviated characters onto the decorative plate.
Since the transparent coating layer is relatively rigid and water-resistant, even when the decorative plate and the colored coating layer are soft and fragile, the transparent coating layer protects the decorative plate and the colored coating layer, thereby improving weather resistance of the decorative portion and maintaining the effect of the decorative groove for a long time.
In the above arrangement, at least one of a grinding process and polishing process may preferably be conducted on the surface of the transparent coating layer.
By performing a grinding process and polishing process on the decorative plate provided with the transparent coating layer thick enough to completely cover the decorative groove of the decorative portion thereinside, the surface of the decorative portion can be made substantially flat without irregularity, thereby enhancing glossiness and transparency of the decorative plate and further emphasizing depth and adding a luxurious touch to the decorative plate.
A second aspect of the present invention is a method of manufacturing a decorative plate according to the first aspect of the present invention.
Specifically, the second aspect of the present invention is a method of manufacturing a decorative plate including a decorative portion formed with a decorative groove extending in spiral from an inner side toward an outer side and being formed in a V-shape cross section by carving a surface of a workpiece, in which a tool having an isosceles-triangle front edge and a right-triangle side edge is used for carving the decorative groove, and, wherein, in the carving step, one of the front edge and the side edge is directed initially in a carving direction and the direction of the tool relative to the carving direction is gradually changed from the one of the front edge and the side edge to the other of the front edge and the side edge.
According to the above second aspect of the present invention, the decorative groove having a slant angle of one of the pair of slanted side different from the other can be carved. Further, the slant angles of the slanted side of the carved decorative groove gradually vary to be equal with each other, thereby producing the decorative plate according to the first aspect of the present invention.
In the above method of manufacturing a decorative plate, the tool may preferably be brought into contact with the workpiece while rotating the workpiece, and the tool may preferably be moved along a straight line offset relative to radius direction of a rotary shaft for rotating the workpiece to carve the workpiece.
According to the above arrangement, when a first end of the moving path of the tool is located at a point adjacent to a rotary shaft and on a radius orthogonal with the moving path, the tool""s edge side faces the carving direction and front side approximately faces the carving direction on the other end of the moving path.
Accordingly, in order to change the attitude of the tool relative to the carving direction, it is not necessary to rotate the tool itself and the decorative groove can be carved only by linearly moving the tool, thereby facilitating carving process of the decorative groove.
In the above producing method of decorative plate, a carving machine that rotates a flat material plate for carving may preferably be used in carving the decorative groove, the material plate having a decorative plate portion to be the decorative plate and a supported portion for supporting the material plate with the carving machine, where the method preferably further include the steps of: before carving, dividing the decorative portion and the supported portion while slightly retaining a connecting portion that connects the decorative portion and the supported portion and simultaneously forming a positioning portion for positioning the material plate relative to the carving machine; and separating the decorative plate portion from the supported portion of the material plate after carving.
Accordingly, when the material plate is supported by the carving machine, the supported portion engages with the carving machine to be secured to the carving machine, so that the carving machine does not touch the surface of the decorative plate portion and the entire surface thereof can be exposed, thereby carving the decorative groove on the entire decorative plate portion.
Further, since the decorative plate portion and the supported portion are divided slightly retaining the connecting portion before the carving process, it is only necessary to cut the connecting portion after the carving process, so that the separating process can be easily conducted with a small force and since no great force is applied on the decorative plate portion during separation, the decorative plate portion is not damaged during separation even when the decorative plate portion is thin
In the above method, the upper surface of the connecting portion may preferably be located at a position below the upper surface of the decorative plate portion.
Accordingly, when the decorative groove is carved on the entire surface of the decorative groove portion, the tool does not touch and cut the connecting portion, thereby preventing a shift in carving position on account of the connecting portion being cut, so that the decorative plate portion can be securely carved even when the decorative plate portion and the supported portion are divided before carving.
In the above method, the workpiece carved with the decorative groove may be used as a molding matrix and the decorative groove formed on the molding matrix is transferred on a synthetic-resin made molding article.
According to the above arrangement, a large number of molded articles formed with the decorative groove can be produced in a short time using molding of synthetic resin superior in processing efficiency as compared to the carving process. Furthermore, the decorative plates having approximately the same appearance can be obtained by metal-plating the produced plate members at one time, so that the decorative plate can be mass-produced.
In the above arrangement, the workpiece having the decorative groove may be used as an electroforming matrix and after forming a conductive layer having electric conductivity on the surface of the electroforming matrix, metal may be thickly plated on the surface of the conductive layer to make an electroforming made of the metal on the surface of the conductive layer.
Mass production of the decorative plate is also possible in the above arrangement and, since the produced decorative plate is made of metal as in the decorative plate produced by carving process, the decorative plate having the same quality as carving precious metal can also be mass produced.
A third aspect of the present invention is a decorative article including a decorative plate according to first aspect of the present invention.
According to the third aspect of the present invention, since the action of the light reflected on the surface of the decorative plate is similar to the light reflected on a bulging surface, the central portion of the decorative plate can appear to be bulging, so that a three-dimensional effect can be achieved with the decorative plate even when the decorative plate is made of a thin plate, which may be attached on a decorative article or directly used as a decorative article to obtain a decorative article having depth and a luxurious touch applied to it.
A fourth aspect of the present invention is a timepiece having the decorative plate according to the first aspect of the present invention as a dial plate.
According to the fourth aspect of the present invention, since the action of the light reflected on the surface of the flat dial plate is similar to the light reflected on a bulging surface, the central portion of the dial plate appears bulging, so that a three-dimensional effect can be achieved on the dial plate even when the dial plate is made of a thin plate, thereby obtaining a timepiece having depth and having a luxurious touch to it.